Developing the Population Estimates
All residents of Oregon's cities, counties, and unincorporated areas are included in the population estimates. Residents include people living in housing units (single-family and multi-family units; mobile homes; special housing units, such as boats, tents, and RVs) and in group quarter facilities (such as college dormitories, nursing homes, jails, and prisons). We count residents as persons living where they consider their usual residence.
Data: To produce the population estimates, we use (1) Administrative data from different agencies/sources and (2) Survey data.
For the administrative data, we use data on birth and death, school enrollment, employment, issued driver's licenses, state income tax exemptions, federal income tax exemptions, and Medicare enrollment data.
For the survey data, we work closely with county and city officials. We request annual information from them and invite them to review our preliminary estimates. We reach out annually (in July) to all counties and cities with our Annual Housing Unit and Population Survey. The city/county officials report the annual changes in the housing units (for single-family, multi-family, and mobile homes), the number of special housing units and the number of persons residing in group quarters facilities.
Method:
For the State, counties, and cities: We use the most recent U.S. Census figures as a base for our model.
To estimate the State population, we use the cohort component method, using natural changes (births minus deaths) and net migration (in-migrants minus out-migrants) to estimate the population growth.
To estimate the county population, we use (1) The cohort component method and (2) The ratio correlation method, modeling the change in the household population as a function of changes in variables such as school enrollment - Medicare enrollment - State/Federal income tax exemptions- Issued driver licenses, and number of employed persons.
We use the housing unit method to estimate the Sub-county (Cities) population. Based on this method, the housing changes are translated to household population counts using the most recent information on vacancy rates and average household sizes from the census and the American Community Survey. Then, it is combined with GQ population changes to compute the total population change. Cities' estimates are controlled, so they sum to the counties's estimates, which are controlled to sum to the State's estimates.
We monitor city annexations throughout the year. We have been notified about annexations by the Office of the Secretary of State. When an annexation occurs, we send an annexation survey to the city official to request the number of residential housing units and population, if any, that were involved in the annexation. If the annexation adds to the city's population, we certify an updated city population, which is done quarterly and published in the supplemental report here.
- With each new release of the annual estimates, the entire time series of estimates is revised for all years back to the beginning of the decade to reflect the increased data availability for some periods ( for example, the COVID-19 and wildfire periods). These revisions increase the accuracy of net changes since the census benchmark (2020 Census).
-When we revise the estimates for previous years, we keep the certified estimates tables for those previous years as they are. So, do not link the revised estimates for the previous years to the annual certified estimates that were published annually for the previous years. The revised estimates for the previous years could be used for research/planning purposes, and they are published in the annual reports in April.
Population Estimates Timeline:
May/June: Reach out (sending letters) to all counties/cities officials to update contact persons.
July: send out Annual Housing Unit and Population Survey (AHUPS) to all contact persons (counties/cities).
November 15: Preliminary estimates are mailed to all counties and cities and published on the website. We give one month for comments/questions (send to popest@pdx.edu).
December 15: Certified estimates are published here.
April 15: The annual population report is published here.
Please visit this page regularly for updates and direct questions/comments regarding the population estimates to Huda Alkitkat, Ph.D. Population Estimate Program manager popest@pdx.edu.